1. Field of the Invention
The present invention relates to a method of joining fastening members for use to assemble or connect articles.
2. Description of the Prior Art
Hitherto, articles have been assembled or connected by ordinarily using fasteners such as bolts, and a variety of washers have been used with the bolts in order to prevent looseness of the tightened bolt, realize a wide area contact, and reliably retain the bolt head if the bolt hole is too large.
In order to be easily transported or stored, or in order to improve the facility of the working operation, a washer of this type has been so arranged, as shown in FIG. 17A, that an underhead portion 21 of a bolt 20 is machined by rolling or the like to make its diameter to be smaller than that of a thread portion 22 so as to receive washers 23 or 24. As an alternative to this, another arrangement has been sometimes employed, in which a washer 23 is fixed by caulking to a seating surface 26 of a bolt head 25 so as to be integrated with a bolt.
However, in the aforesaid case shown in FIG. 17A, the rolling work must be additionally performed at the time of manufacturing the bolt 20, and therefore the cost of the product rises excessively. As a result, a problem arises in that a desire of supplying cheap products to the market cannot be achieved. What is worse is that whenever the combination of the washers 23 and 24 is changed, the machining jig must be changed and this changing work takes a too long time. In addition, the strength of the underneck portion 21 formed to have a small diameter becomes unsatisfactory, causing a problem in that fastening cannot be stably performed. Furthermore, since the thread portion 22 is omitted from the underneck portion 21, the aforesaid arrangement cannot be adapted to fasten a thin member.
In the case shown in FIG. 17B, the arrangement so made that the washer 23 is temporarily fixed to the bolt 20 will cause the member, which is the subject of the fastening work, to be damaged by burrs or the like left on the surface of the washer 23 when the bolt 20 is revolved, if the side of the washer 23 is adversely selected when it is temporarily fixed to the bolt 20.
In particular, the aforesaid structures involve a fact that the washer cannot be changed to another kind of washer at the time of the fastening work, that is, the washer cannot be removed from the shaft portion or the thread portion of the bolt, causing a necessity in that a required number of sets, each of which is composed of a bolt and a nut, are prepared depending upon the object or the portion in which they are used. Therefore, a problem arises in that the cost to perform the fastening work cannot be reduced and storage and the stock control cannot be easily performed. Furthermore, since the washer cannot be temporarily fixed to the shaft portion or the thread portion of the bolt, the washer will undesirably fall from the thread portion of the bolt if the nut is received by the bolt in a case where the bolt faces downwards. What is worse is that an operator must labor the task at the time of performing the fastening work in a portion into which the hand cannot be easily introduced or a portion at which the operator cannot take a comfortable position. As a result, a problem on a viewpoint of the working condition takes place.